Amplifying system



- 1m- 1. mm W. H. T. HOLDEN 1,142,251

AIIPLIFYING SYSTEM Filed Ma 26. 1926 c, K A L r I 5; aqlllllll A TTORNEY cuit of the vacuum tube V supplying energy to the input circuit of vacuum tube V includes the plate of the vacuum tube V the condenser the resistance R the battery B and the filament of the vacuum tube V The input circuit of the vacuum tube V similarly includes the resistance R and the battery B the resistance R also being of a magnitude suificient to produce the necessary bias for the grid of the vacuum tube V In accordance with this invention, a condenser C and an auto-transformer L are associated with the vacuum tube V Condensers and auto-transformers are similarly connected to the vacuum tubes V and V Each condenser and auto-transformer are in series relationship with each other between the plate and grid of the associated vacuum tube. The auto-transformer L is so arranged with respect to the condenser C that the flow of current through the circuit including the auto-transformer L and the condenser C is ofa magnitude equal to that flowing in the vacuum tube by virtue of the capacity between the plate and the grid there- "of, but is opposite in phase to the current flowing in the winding transformers, such as windings a and b the windings of transformers L flowing within the vacuum tube. More specifically the current flowing in the winding a of the auto-transformer L is equal in magnitude and opposite in phase to that Inasmuch as the current flowing through the condenser C and that flowing in the vacuum tube V by virtue of the ca acity between the plate and the grid, are 0th equal in magnitude and op- 'posite in phase, they will balance and neutralize each other, and consequently they will have no effect upon the faithful amplification of signals by said vacuum tube.

It will be understood that each of the auto- L,, may be of the aircore type or of the iron-core type and that this transformer is employed primarily to obtain the reversal in phase of the current to be fed back through condenser G Of course, of transformer L may or may not have the same number of turns; yet if condenser G which is associated with transformer 7L has a capacity equal to the inherent capacit between the plate and grid of vacuum tube then it becomes desirable Obviously, and L may also be proportioned in accordance with the to have a turn ratio of unity.

ratio between the capacities of condensers U, and C and the inherent capacities be tween the plate and grid electrodes of vacuum tubes V and V respectively.

Thus, neutralization is accomplished in this invention as follows: Current flowing throughthe circuit including K resistance R and battery B causes the application of an alternating current voltage between the grid and filament of vacuum tube V Some alternating current will, nevertheless, flow through winding a battery 13,, ground and back to the filament of vacuum tube V Accordingly, there will'be a voltage induced in winding 6 which is substantially equal to the voltage across winding a though opposite in phase. This voltage is transmitted through condenser C and will neutralize and render ineffective the feed-back arising from the inherent capacity between the plate and grid (of vacuum tube V Obviously, the same principles apply in the consideration of the circuits associated with vacuum tubes V and V Untuned or aperiodic amplifiers are suitable in many systems where tuned and periodic amplifiers are especially unsuitable. It is to be understood that it is one of the features of this invention to provide an untuned or aperiodic amplifier which has neutralizing means associated therewith, so that the effect of inter-electrode capacity is completely eliminated.

While. the invention has been disclosed in one particular embodiment, which is deemed desirable, it is to be understood that it is capable of ex bodiment in other and widely varied organizations, without departing from the spirit of the invention and the scope of the appended claims.

What is claimed is:

1. In an untuned, multi-stage amplifier for amplifying currents of all frequencies within a wide range of the frequency spectrum, a plurality of vacuum tubes each having a late, a filament and a grid, impedance means including a condenser for coupling each pair of said vacuum tubes, a plurality of inductive reactances each of fixed magnitude, a plurality of capacitative reactances each of fixed magnitude, each inductive reactance being in series relationship with the corresponding capacitative reactance in a circuit between the plate and grid of the corresponding vacuum tube, a source of potential connected to the plate of each vacuum tube through the inductive reactance associated therewith, the current flowing through the inductive and capacitative reactances associated with each vacuum tube and the current flowing in each vacuum tube by virtue of the capacity existing between the plate and grid thereof being equal in magnitude and opposite in phase.

2. In a multi-stage, impedance coupled amplifier of the untuned or aperiodic type for amplifying currents of all frequencies within a broad band of the frequency spectrum, the combination of a plurality of vacuum tubes each having a plate, a filament and a grid, a plurality of condensers, a plurality of untuned auto-transformers, one condenser and one auto-transformer being in series relationship with the plate and grid of the corresponding vacuum tube, impedance means including a condenser for coupling each pair of said vacuum tubes, and means for transmitrality of untuned auto-transformers, d a c tween the plate and ting a current through the condenser and the i corresponding auto-transformer associated with each vacuum tube which will be equal in magnitude and opposite in phase to the current flowing within the tube by virtue of the inherent capacity existing between the plate and grid of said tube.

3. In a multi-stage, impedance coupled amplifier of the untuned or aperiodic type for amplifying currents of a broad band of frequencies, the combination of a plurality of vacuum tubes each having a plate, a filament and a grid, a plurality of condensers, a pluone co11- uum tube, impedance means including a condenser for coupling each .pairof said vacuum tubes; and means for establishing a neutralizing current through each series condenser and auto-transformer which'shall be equal in magnitudeand opposite in phase-to the current flowing within the tub the inherent capacity between gridthereof.

In testimony the plate and whereof, I have signed my name to this specification this 25th day of May 1926. y 7

WILLIAM H. TJHOLDEN.

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